This is ReachMD, and you are listening to Conversations on Colorectal Cancer, sponsored by Lilly. On this episode, titled “How mCRC Tumor Sidedness Guides Treatment Decisions” we will hear from Dr. Richard Kim from Moffitt Cancer Center.
The sidedness of the tumor in colorectal cancer has now become very important in our decision-making. It is a clearly known fact that the sidedness is a prognostic marker. So, if you have a right-sided tumor, you tend to do worse than the left-sided tumor. Not only that, the sidedness could be a predictive biomarker in which biologic we use. Based on the CALGB 80405 study and the FIRE-3 study, if you have a right-sided tumor, there is no benefit of giving anti-EGFR drugs with chemotherapy even in RAS wild-type patients.
However, in left-sided tumor, there is data that giving anti-EGFR drugs may have overall survival benefit over anti-VEGF drugs. Therefore, if you have a newly diagnosed left-sided tumor, RAS wild-type, as per NCCN and ASCO guideline, they give you, actually, a choice of either using bevacizumab-based chemotherapy or anti-EGFR-based chemotherapy, and that will be determined upon the treating physician based on the discretion and the toxicity profile. However, based on those data, if you look at the ESMO guideline, it is recommended that in left-sided tumor, RAS wild-type, that you give EGFR-based chemotherapy. Therefore, there is a controversy involving the treatment of the left-sided tumor. However, in the right-sided tumor, it is clear that anti-EGFR drugs do not respond.
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